In vehicles such as trucks and other off the road vehicles, it is common to utilize the power from the transmission to operate various components such as hydraulic pumps and mechanical devices.
Such mechanisms are known as power take-off devices and generally comprise a housing in which gears are supported. The housing is mounted on the transmission at an opening generally provided by the transmission manufacturer and one of the power take-off gears projects through the opening into engagement with the gear of the transmission to receive the input from the transmission. The power take-off device also includes an output shaft through which the output is provided and intermediate gears connecting the one gear and the output shaft. The device also includes means for engaging the gears to engage the power take-off. A typical shifting device is shown in U.S. Pat. No. 3,270,580.
Because of space limitations in the vehicle, it is desirable to provide compact power take-off devices that have a small envelope.
In one commonly used design, the power take-off includes a cast iron housing with a fixed shaft on which an input gear is rotatably mounted by bearings. A second gear also mounted on bearings is axially movable on the fixed shaft for engagement with a third gear on an output shaft. In order to provide a range of horse power capacities and torque, it has been heretofore necessary to design each power take-off for a particular use. In order to repair or attempt to change the gear ratios, it has been necessary to remove the fixed input shaft, replace the bearings and the gears.
Because the gears are mounted on bearings between the gears and the shafts, there is a limit to the minimum radius of the gears that can be changed and accordingly there is a limit to the range of horse power or torque that can be accommodated within the same housing.
Among the objects of the invention are to provide a power take-off which is compact, wherein a single housing can be utilized with various combinations of gears to provide a wide range of horse power capacities and torque; which is light in weight; which provides greater sound diffusion; which has higher impact strength; which incorporates novel shifting mechanisms of either the air or the mechanical type; wherein the speed ratio and transmission gear sets can be readily changed; which has improved bearing and gear design; which is more quiet in operation and wherein the various parts of the power take-off are accessible readily for repair; and which requires a minimum size or envelope of the housing.
In accordance with the invention the power take-off comprises a housing having spaced walls, an input shaft that is rotatably mounted in a first set of aligned openings in the walls and an output shaft rotatably mounted in a second set of aligned openings in the walls. A pair of gears is interposed between the walls and rotatably mounted on the input shaft. The housing has an opening through which said one of the pair of gears extends for engagement with a gear of a transmission. A third gear is fixed on said output shaft and meshes with the teeth on the other gear. The first and second gears have annular gear portions. An annular clutch member having internal teeth is movable from a position wherein the internal teeth engages a gear portion of one of the first and second gears to a position wherein the internal teeth engage the second gear portions on both the first and second gears.
The opening in the housing is sufficiently large to permit removal of the first and second gears by first removing the input shaft axially so that the first and second gears are thereby released.
The housing is preferably die cast and the walls of said housing have tapered surfaces extending inwardly toward one another. A first washer is interposed between the first gear and one of the walls and a second washer is interposed between the second gear and the other of the walls. The washers have openings through which the input shaft extends and each washer has spaced wall surfaces which taper such that the washers provide parallel surfaces for engagement with the first and second gears, respectively, thus eliminating a machining operation.
The take-off device also incorporates novel interchangeable shifter mechanisms for engaging and moving the clutch. In one form the shifter mechanism is air operated and in another form the shifter mechanism is mechanical for operation by cables or other linkages.